288 APPENDIX. 



the intestine and skin, encircles the body with a continuous canal of 

 equal calibre in every portion of its long circuit (PL II. A. fig. .5). 

 It is uncertain whether these side-vessels are connected by smaller 

 transverse inosculations : I believe they are, and that the pale lines 

 which we observe to cross the body in some species, at short and 

 regular intervals, are produced by these vessels of communication 

 (PI. II. A. fig. 1). On examining fig. 5, another vessel will be 

 seen winding down the middle, along the surface of the alimentary 

 canal, in an undulating line. That it has any connexion with the 

 centre of circulation or lateral vessels, I cannot affirm, for I could 

 neither trace its origin nor its place of termination, nor can I per- 

 ceive that any vessel goes from it ; but we may be allowed to infer, 

 from its analogy with the Planarice^y that it belongs to the circu- 

 lating, and not to a nervous system. I have never detected the 

 slightest appearance of a fluid in motion in any of the vessels ; and 

 were I to call the central vessel an aorta, and to decide that the 

 lateral vessels were for the purpose of returning the refluent fluid to 

 the heart, I might justly be censured for indulging in a fancy which 

 has no observation in its support. We are too liable to assign to the 

 organs of these lower creatures the names of what we deem their 

 analogues in higher classes, and with the name to associate an idea 

 of sameness or identity in their functions, — a propensity which has 

 not seldom led to error. 



The Nemertes live under stones and in mud between tide-marks : 

 they avoid the light, and love obscurity. They are numerous in in- 

 dividuals, but how they are propagated is yet conjectural. At certain 

 seasons I have seen within the body small roundish oviform grains 

 lying unconnected with any particular viscus, but of the real nature of 

 these, no observation has enabled me to form an opinion. Specimens 

 have also occurred in which there seemed to be the commencement 

 of a separation of the body into two or more parts, but these marks 

 of division might be the effect of injury. The species are very 

 tenacious of life ; if cut into several pieces, each lives and moves, and 

 perhaps in time each will grow up to a complete and perfect worm. 

 When placed in fresh water, they show, by instant contortions, how 

 painful and poisonous is this fluid to them. They soon break into 

 pieces, disgorge portions of the viscera, and speedily die and dissolve 

 into a soft jelly. 



On the structure of this Tribe, see H. D. S. Goodsir in Ann. ^ 

 Mag. Nat. Hist. xv. 379. 



Astemma rufifrons (page 19). 



Deposits its spawn in a rope about an inch long, in which the 

 white spherical ova are contained. The young, on their birth, are 

 of an oval form, flattened, begirt with cilia ; and they have two black 

 eyes in front, one on each side. — Daly ell. 



* See figures illustrative of this in Roget's Bridgew. Treat, ii. 250. fig. 346 ; 

 and in Cyclop, of Anat. and Physiology, i. 653. fig. 327. 



